Cinematography is the camera work in film, this could be angles, shot types and the movements the camera may do. The purpose of this is to convey a meaning in a different way to other elements of film. For example a slanted shot type could imply that something about the character/situation is wrong or something is off. And a a close-ep shot type could imply that the situation is tense in the scene. Camera movements may be used when introducing a character to possibly inform the viewer of the characters personality/behaviour without any dialogue/monologue.
A cinematographer is the person operating the camera, this person is the one who is controlling the use of cinematography. The Director and Cinematographer may converse and discuss about the different ways they can make this scene and the best way to do it. Cinematographers also oversee the technical aspect of camera, focus, lens types, focal lengths, measuring focal distance between object and observer, even though the director is also control of this and can decide how they want to do the shot to convey the intended meaning in the best possible way but the cinematographer carries out what the director wants for the scene